Saltatory and Sinusoidal Fetal Heart Rate (FHR) Patterns and significance of FHR 'Overshoots'

Electronic fetal heart rate monitoring (EFM) in labour began its evolution in 1950s and became commercially available in late 1960s. EFM was introduced to identify those fetuses that were exposed to intrapartum hypoxia and were not able to tolerate ongoing hypoxic stress. Failure of compensatory mechanisms could lead to the development of respiratory and/or metabolic acidosis secondary to the intrapartum hypoxic insult, which if left undetected and treated, may have severe consequences. These include long-term implications such as learning difficulties, cerebral palsy and in some cases, increased risk of perinatal deaths. Use of EFM in high-risk labour has been associated with a significant reduction in fetal mortality rates and early onset neonatal seizures. The purpose of this article is to revisit the relatively uncommon findings of sinusoidal, overshoot and saltatory patterns in a cardiotocograph (CTG), their clinical implications and the approach to managing them in labour.